The objectives of the proposed work are to study the effects of S. mansoni excretory-secretory (ES) products in vitro in the absence and presence of mecahnical barriers, to isolate ES products and test them for their influence on worm behavior, and to partially characterize ES products that influence worm behavior. Bioassay studies in our laboratories using chambers containing linear channels suggest that all combinations of S. mansoni adult male and female worms attract each other in vitro in the absence of mechanical barriers, and that males isolated in perforated dialysis tubing chimneys attract females, presumably by the release of ES products. Systematic in vitro studies will be carried out to determine other interactions between schistosomes, and it will also be determined whether adult worm pairs attract or repel other males or females. Videotaping will be used to track worm behavior. Schistosomes at different ages will also be examined to determine whether they attract or repel other schistosomes in vitro. Studies will also be carried out to isolate ES products from S. mansoni and to test them in the bioassay chambers for their influence on worm behavior. Preliminary studies in our laboratories have shown that both males and females emit lipophilic ES products, although the role(s) of these products are not yet known. Appropriate chemical studies will be undertaken to partially characterize the active ES products. Knowledge about biologically active ES products could lead to convenient, economical preventive measures against schistosomiasis, either in the form of chemical or immunological blocking agents.